Downing Street yesterday apologised for its failure to acknowledge that much of its latest dossier on Iraq was lifted from academic sources, as the affair threatened to further undermine confidence in the government's case for disarming Saddam Hussein.

MPs and anti-war groups were quick to protest that other features of Whitehall's information campaign are suspect at a time when MI6 and other intelligence agencies are privately complaining at the way No 10 has been over-egging intelligence material on Iraq.

It emerged yesterday that the dossier issued last week - later found to include a plagiarised section written by an American PhD student - was compiled by mid-level officials in Alastair Campbell's Downing Street communications department with only cursory approval from intelligence or even Foreign Office sources.

Though it now appears to have been a journalistic cut and paste job rather than high-grade intelligence analysis, the dossier ended up being cited approvingly on worldwide TV by the US secretary of state, Colin Powell, when he addressed the UN security council on Wednesday.

Downing Street yesterday toughed it out, insisting that what mattered was that the facts contained in the document were "solid" and helped make the case Tony Blair rammed home on BBC Newsnight. But the middle section of the dossier, which describes the feared Iraqi intelligence network, was taken, much of it verbatim, from the research of Dr Ibrahim al-Marashi without his knowledge or permission.

"In retrospect we should have acknowledged [this]. The fact that we used some of his work does not throw into question the accuracy of the document as a whole, as he himself acknowledged on Newsnight last night, where he said that in his opinion the document overall was accurate," the No 10 spokesman conceded. "We all have lessons to learn," he added. The four officials originally named on the website version of the 19-page dossier include Alison Blackshaw, Mr Campbell's senior assistant, and Murtaza Khan, described as a news editor on the busy Downing Street website.

Professor Michael Clark, director of the International Policy Institute at King's College London, said presenting such intelligence material "invalidates the veracity" of the rest of the document. The shadow foreign secretary, Michael Ancram, called for a cabinet minister to oversee government information on Iraq.

Even before the latest row some Whitehall officials were protesting that MI6 and other intelligence material was being used selectively by Downing Street. A well-placed source made it clear that the dossier had been the work of Downing Street and the Coalition Information Centre, the body set up after September 11 to put the US-British case on the war against terrorism. The source dismissed a key section of the dossier as full of "silly errors".

Glenda Jackson, the Labour former minister, was one of several MPs to protest that the government was misleading parliament and the public. "And of course to mislead is a parliamentary euphemism for lying," Ms Jackson told Radio 4's Today programme.

Dr al-Marashi expressed "surprise" at the lack of a credit for his work, as did other authors whose research was quickly identified. One anti-war group, Voices in the Wilderness, identified a passage from No 10's September dossier directly traceable to Saddam Secrets, a book by Tim Trevan published in 1999.

The Middle East Review of International Affairs, from which Dr al-Marashi's work was lifted, is based in Israel, which makes it a suspect source to even moderate Arab opinion, and another reason why the origin of the information should have been listed.

In Whitehall one official who regularly sees MI6 reports said that Britain's knowledge about Iraq until recently had been very poor. But another claimed there has been a recent transformation: "What has happened in the last nine months is that there is now strong intelligence coming through."

Disturbing reports

The government has issued three reports in the past six months, trying to establish a case for action against Iraq. Each one has drawn progressively more criticism.

September The 50-page dossier Iraq's Weapons of Mass Destruction: The Assessment of the British Government relied heavily on input from the Foreign Office and MI6.

The material was damning, but most of it turned out to be years old. British journalists in Baghdad visited several "facilities of concern" highlighted in the report and found nothing sinister. UN weapons inspectors later visited the same sites and uncovered nothing.

December The 23-page Saddam Hussein: Crimes and Human Rights Abuses provided a horrifying account of abuses but was widely criticised by human rights groups, MPs and others for recycling old information.

At the launch, the Foreign Office had on the platform an Iraqi exile who had been jailed by President Saddam for 11 years. Later, he disclosed that handcuffs he had worn had been made in Britain.

January 30 Iraq: Its Infrastructure of Concealment, Deception and Intimidation, was a Downing Street production. The first sentence of the report said it was based on a number of sources, including intelligence material, but it turned out that much of it was lifted from academic sources. Glen Rangwala, an academic who blew the whistle on the dossier, said yesterday: "It really does cast doubt on the credibility of the intelligence that has been put to us."